(1) Field of the Invention
The present invention relates to a tester for an optical device and, more particularly, to a technique for conducting a characteristics inspection in which an optical device is allowed to emit light and a light receiving element measures an output of the light.
(2) Description of the Related Art
In the field of optical discs, recently, there have been rapidly popularized optical disc drives for compact discs (e.g., CD-ROM, CD-R, CD-RW) and digital versatile discs (e.g., DVD-ROM, DVD-RW, DVD-DAM).
An optical pickup as a key component of an optical disc drive is strongly demanded to satisfy the following: high output in order to respond to high speed recording, enhanced function in order to conform to both specifications of a CD and a DVD, and size reduction in relation to size reduction of the optical disc drive.
Therefore, optical devices used in the optical pickup adopt various package structures, e.g., a package structure in which heat dissipation is improved for realizing high output, a multi-pin structure for responding to enhanced function, and a package structure with narrow width, for realizing size reduction.
In order to conduct a test on these optical devices, a tester must respond to the various package structures.
FIG. 11 is a sectional view of a conventional optical device. FIG. 12 is a sectional view of a conventional tester for conducting a test on an optical device.
An optical device 100 illustrated in FIG. 11 includes a lead frame 110 in which a semiconductor laser element 111 and a resin frame body 112 are provided. In the optical device 100, an external connection terminal is provided on a bottom face of the lead frame 110 and the semiconductor laser element 111 emits outgoing light 113 upward from a top face of the lead frame 110.
The tester illustrated in FIG. 12 includes a socket base 11 mounted on a first board 10, and a cover 12 coupled to the socket base 11 in an openable/closable manner. The socket base 11 is used for placing thereon the optical device 100 illustrated in FIG. 11, and has a terminal 13 on its top face. The terminal 13 comes into contact with the external connection terminal provided on the bottom face of the optical device 100.
The cover 12 incorporates therein a second board 17 on which a light receiving element 14 and an optical filter 15 are provided. The light receiving element 14 is used for measuring output of outgoing light emitted from the semiconductor laser element 111 of the optical device 100. The optical filter 15 is used for attenuating the output of the outgoing light emitted from the semiconductor laser element 111. The light receiving element 14 is electrically connected to the first board 10 through the second board 17 and a flexible substrate (not illustrated).
A characteristics test for the optical device 100 is conducted as follows. First, the optical device 100 is placed on the socket base 11, and the terminal 13 of the socket base 11 is brought into contact with the external connection terminal provided on the bottom face of the optical device 100. Then, the cover 12 is closed, and the optical device 100 is put in the tester so as to be interposed between the socket base 11 and the cover 12.
The tester in which the optical device 100 is put is placed in a thermostatic furnace kept at a constant temperature. In this state, an electric current is supplied to the optical device 100 through the first board 10, so that the semiconductor laser element 111 is allowed to emit light. In the optical device 100, the semiconductor laser element 111 emits the outgoing light 113 upward, i.e., toward the light receiving element 14 incorporated in the cover 12. At the constant temperature, the light receiving element 14 receives the outgoing light 113 emitted from the semiconductor laser element 111 to thereby measure output of the outgoing light 113.
Herein, a driving current to be supplied to the optical device 100 is controlled to keep the output of the light constant and allow to emit the light over a predetermined period of time. Then, an amount of change in the driving current during the period of time is measured and, on the basis of the result of measuring the change amount, electrical characteristics of the optical device 100 are assayed. For example, JP10-19663A discloses a conventional technique for such a tester.
However, the aforementioned tester for an optical device has the structure that the terminal 13 coming into contact with the external connection terminal of the optical device 100 is provided on the top face of the socket base 11 and the light receiving element 14 is incorporated in the cover 12 provided so as to oppose the top face of the socket base 11. Therefore, the tester has a problem of limitation in type of optical devices to be measured. In other words, the aforementioned tester can measure only an optical device having a structure that an external connection terminal is provided on a bottom face of the optical device and a semiconductor laser element emits light upward from a top face of the optical device.
At present, there are various types of optical devices, e.g., an optical device in which an external connection terminal is provided on a top face of the optical device and light is emitted upward from the top face of the optical device, and an optical device in which light is emitted sideward along a top face of the optical device. Therefore, it is necessary to provide a dedicated tester for each optical device. However, it is difficult to provide a dedicated tester for each optical device from the viewpoint of cost reduction.